Demulsification of oil emulsions with a mixture of polymers and alkaline earth metal halide

ABSTRACT

A process for recovering oil from either water-bituminous petroleum emulsions or from crude petroleum emulsions having a pH of 10 or less by adding thereto an optimum amount of non-ionic, water soluble polyethylene oxide polymers at a pH of 10 or less, and separating the oil from water. To resolve bituminous petroleum emulsions, the process is carried out at between 150° F and 210° F and a diluent is added to reduce the petroleum viscosity. The minimum effective concentration of the polymers used decreases as their molecular weight increases. 
     In a modification of the process, an effective amount of an alkaline earth metal halide such as calcium chloride is added to improve coagulation and separation of any clay present.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is concerned with the resolution of water-bituminousemulsions and conventional petroleum emulsions by treatment withpolyethylene oxide resins of optimum molecular weight at a controlled pHrange. The invention is also concerned with the separation of water frombitumen which has been brought to the surface in the form ofwater-in-oil or oil-in-water emulsions by an in situ recovery process.

2. STATEMENT OF THE PRIOR ART

Numerous hot water extraction methods exist for separating crude oilfrom bituminous sands (tar sands, oil sands and the like) which involvemixing such sands with hot or cold water and separating the sand fromthe resulting emulsions.

The technical difficulty encountered with emulsions produced by an situoperations is that the liquid mixture is a highly stabilized emulsionwhich is difficult to break with standard treating chemicals.

The attempts made in the prior art to break emulsions resulting from hotwater extraction processes are represented, inter alia, by thetechniques described in U.S. Pat. Nos. 3,808,120; 3,607,721, and3,487,003.

U.S. Pat. No. 3,808,120 describes a method for separating at least waterand solids from the froth produced in a hot water process for separatingbitumen from tar sands by treating the froth in at least one cyclonezone after which it is treated in at least two centrifuging zones.

In U.S. Pat. No. 3,606,721, a process for the removal of solids andemulsified water from a bituminous emulsion is disclosed which comprisesdiluting the emulsion with a hydrocarbon diluent; maintaining theresulting mixture in a settling zone, removing the emulsion whensubstantially free of solids and emulsified water from the top of thesettling zone, withdrawing settled sludge from the bottom of thesettling zone and centrifuging the withdrawn sludge to separate bitmenand diluent from the settled solids and the emulsified water.

U.S. Pat. No. 3,487,003 describes a method for reducing the solidscontent of an effluent discharge from a hot water process for separatingoil from bituminous sands by adding a flocculating agent which may beorganic inorganic or even a polyalkylene oxide of undisclosed molecularweight to this effluent; adjusting the pH of the effluent to less than7.5 or more than 9 to effect flocculation of at least a portion of thesolids therein; centrifuging the effluent now containing flocculatedsolids recovering the effluent discharge substantially reduced in solidscontent. This method treats not an oil-in-water emulsion but rather aneffluent comprised of the effluent from the sand tailings layer and themiddlings layer. Further, there is no appreciation therein of thenecessity for maintaining the temperature within a given range duringtreatment with the flocculating agent.

Also generally known in the art is the concept of adding certainchemicals such as organic sequestering agents and organic flocculatingagents to petroleum and other emulsions.

The cost of such chemicals amounting to around $1.00 to $1.30 per barrelof bitumen coupled with other operating and capital equipment costsprecludes the obtaining of a final product which is economicallyequivalent to the cost of conventionally produced crude oil.

SUMMARY OF THE INVENTION

The main object of this invention is to achieve functionaldemulsification of emulsions at a minimal cost.

This object is attained by the present invention which resides in theconcept of demulsifying emulsions by adding thereto at a pH of 10 orless from 10 to 60 parts per million of non-ionic water-solublepolyethylene oxide resins having a molecular weight in the range of100,000 to 7,000,000 thereby causing the oil to separate from water andany clays present. The ethylene oxide polymers remove substantially allthe clays from the oil and deposit them in the water phase.

In another aspect of the invention, there is achieved thedemulsification of oil-water emulsions recovered by the treatment ofbituminous sands.

In a further aspect of the invention, a bituminous petroleum emulsion istreated with the aforementioned resins; diluted with a liquidhydrocarbon diluent; and centrifuged under carefully controlled feed andwater recycle rates.

Other aspects of this invention will be apparent to those skilled in theart from a reading of this disclosure and of the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The process of the invention can be used to treat oil-bearing fluidsderived from bituminous sands and conventional crude petroleum emulsionby various methods. In one such method, steam is injected in the sandsformation through a center well in a multi-well pattern and the fluidsare produced in the adjoining wells. The produced fluids are stabledilute oil-in-water emulsions containing an average of 10% oil withvariations in oil phase concentrations from 8 to 25%.

The produced fluids can be treated in a conventional horizontal treateroperated at about 250° F and about 20 psig pressure to separate the oilfrom the water phase. In the present process, to the resultingoil-in-water emulsion is added from about 10 to about 60 parts permillion of an ethylene oxide polymer having a molecular weight in therange of 100,000 to 7,000,000. Suitable polymers are those marketed byUnion Carbide Corporation under the trademark name of "Polyox". Theseresins are high polymers with the structure (O-CH₂ CH₂)_(n) with thedegree of polymerization "n" ranging from 200 to about 100,000 giving amolecular weight range of 100,000 to about 7 million. Best performancedefined as the obtaining of separated oil containing less than 3 percentof water and separated water containing less than 0.5 percent oil isachieved when the temperature of the treated material is in the range of150°-210° F or below temperatures at which the resin becomes waterinsoluble. In the practice of the invention, produced fluid from a wellor other source is flowed into a heat exchanger to bring it within thedesired temperature range and then into a treating vessel. The polymersand from 0 to 50 percent of a hydrocarbon diluent such as toluene,diesel oil, fuel oil, kerosene, etc., are added and mixed with thebitumen-water emulsions.

In the process of the invention, the system is maintained at a pH of 10or less by the addition of mineral acid. A suitable pH range is 4 to 10.

While not wishing to be bound by any specific theory, the mechanismunderlying operation of the subject resins as demulsifying agents forproduced fluids is believed to be as follows. The produced fluidemulsion consists of water as the continuous phase and bitumensurrounded by fine clays as the dispersed phase. It is the presence ofthe fine clays which are more likely held to the bitumen droplets by astatic charge that results in the formation of a light bitumen-wateremulsion. The subject resins exhibit a stronger attraction for the claysand hence remove clay surrounding the bitumen droplets thus leaving anemulsion which will coalesce and separate naturally. Further the removalof the clays leaves the emulsified bitument accessible to the dilutingaction of the diluent, a condition which favors reasonable separationtimes.

With a view to more fully describing the present process, the followingexamples are given in a non-limiting sense.

EXAMPLE 1

The sample used consisted of production fluids from wells which areessentially all crude oil in water (o/w) type, highly clay stabilizeddilute emulsions. The oil phase concentrations of the fluids variedbetween 8 and 24 (v/v) and had a pH of 7.2 - 7.9. The additive used wasPolyox-FRA -- A high molecular weight polymer of ethylene oxide(molecular weight 7,000,000). (Product of Union Carbide Corporation).

An aqueous solution (0.2% w/v) of "Polyox" was used for evaluationpurposes. The resin (0.2g) was dissolved in water (100 ml) by firstdispersing it in boiling water. Gelling of the solution should beavoided while dissolving the resin.

The effect of the chemical agent on the emulsions was evaluated using abottle-test procedure. The reagents were added to the 16-ounce widemouth glass jars equipped with "Bakelike" screw caps in the order givenbelow, and were mixed on a wrist-action mechanical shaker for fiveminutes. The jars were then placed in a gravity oven maintained at 70°C±2° C.

Formation of interface with time was observed over a period of 24 hoursor longer.

The materials were added in this order:

1. Diluent (Toluene or Diesel)

2. Production Fluid

3. Chemical Agent

In a typical test, 10 ml of 0.2% aqueous solution (66 ppm of fluidbases) of Polyox-FRA agent was added to 300 ml of production fluid (16%oil cut) containing 34 ml of toluene as diluent. The contents of the jarwere mixed for five minutes and then placed in an oven for observation.The volume of water separated was determined by aligning a calibrated16-ounce jar with the interface of a sample jar.

Several evaluation tests were performed using Polyox-FRA agent onindividual as well as combined fluid samples from wells.

Other test results indicated that Polyox-FRA consistently produceddemulsification of production fluids at dosages down to 10 ppm with bestresults at 66 ppm. In all these tests maximum water separation andinterface formation occurred within less than 12 hours.

The effect of Polyox-FRA agent on the production fluids was also testedat high fluid temperatures (90°-95° C) using a magnetic stirrer and hotplate arrangement.

EXAMPLE 2

A sample of water-in-oil type emulsion (about 30% oil cut) from theBoundary Lake formation was treated with Polyox-WSR-301 (molecularweight about 4,000,000) at a concentration of 10 ppm (relative to totalfluid). The treated sample was demulsified upon standing in an oven at70° C for less than 24 hours. The resulting oil cut contained no water(Dean and Stark Method) and the liberated water was transparent andcolorless. A controlled sample (no chemical added) exhibited nodemulsification under identical conditions.

In a modification of the invention, an effective amount ranging from 0to 20,000, usually 100 to 2,000, parts per million of emulsion, ofcation as may be available from an alkaline earth metal halide such ascalcium chloride, is added to improve coagulation and separation of theclay. The preferred amount depends on the temperatures, type of claypresent, the pH of the system, type of cation added, and the existingconcentration of cations. Preferably such addition is effected by addingthe halide to the emulsion in the form of an aqueous solution so as tofurther dilute the emulsion. In this modification of the process, thesurface active effect of the polyethylene oxide resins improves theseparation of the oil from the clay when the halide begins to coagulatethe clay. This modification of the invention is illustrated by thefollowing examples.

EXAMPLE 3

Clay enriched middlings containing 0.03 grams per 100 grams ofpolyethylene oxide resin per 100 grams of middlings were diluted by theaddition of water containing 750 ppm of CaCl₂. Air was admitted in thevessel and after aeration the bottoms were centrifuged. It was observedthat the precipitate at the bottom of the centrifuge tube was layered.It appeared that sand grains were at the bottom followed by darkenedclay and on top was a dark colored material which appeared to beprincipally bitumen. An analysis was made on the top layer after dryingin an oven at 85° C. The top layer contained 47.6% bitumen, dry basis.

EXAMPLE 4

Another test was run using 0.01 gm polyethylene oxide in 300 ml ofdiluted clay-bitumen simulated middlings. 100 ml of middlings were used.A blend of 100 ml middlings + 0.01 gm "polyox" was shaken up thendiluted with 200 ml water, shaken up, and finally 0.15 gm of CaCl₂ wasadded as a 5% solution. This was shaken and allowed to settle. Themixture broke into 3 layers. A heavy sediment on the bottom, a clearmiddle layer of water and a heavy froth on top. The froth was skimmedoff, allowed to dry in an oven at 85° C and an analysis was carried out.The pH of the aqueous system was 10.2. The bitumen content of the toplayer of froth was 30.9%.

It is to be understood that the foregoing specific examples arepresented by way of illustration and explanation only and that theinvention is not limited by the details of such examples.

The foregoing is believed to so disclose the present invention thatthose skilled in the art to which it appertains can, by applying theretocurrent knowledge, readily modify it for various applications.Therefore, such modifications are intended to fall within the range ofequivalence of the appended claims.

What is claimed is:
 1. A process for recovering oil from oil-in-waterand water-in-oil emulsions wherein said emulsions contain clay tendingto stabilize said emulsions, said process comprising in combinationdemulsifying said emulsions by adding thereto from 10 to 60 parts permillion of non-ionic, water-soluble, polyethylene oxide polymers havinga molecular weight in the range of 100,000 to 7,000,000, together with100 to 20,000 parts per million of an alkaline earth metal halide in anaqueous solution and separating said oil from said water and said clay.2. The process of claim 1, wherein said emulsions are the fluidsproduced by an in-situ recovery operation.
 3. The process of claim 1wherein said oil is present in an oil-in-water emulsion.
 4. The processof claim 3, wherein said oil originates from bituminous sand.
 5. Theprocess of claim 1, further including the steps of diluting saidemulsion after the addition of said polymers and said halide with from30 to 50 volume percent of a hydrocarbon diluent, maintaining thetemperature of the resulting mixture between 150° and 210° F; andcentrifuging said mixture to separate said oil from said water and saidclay.
 6. The process of claim 5, wherein sid diluent is diesel oil ortoluene.
 7. The process of claim 1, carried out at a pH not above
 10. 8.The process of claim 1, wherein said polymer has a molecular weight ofaround 4,000,000.
 9. The process of claim 1, wherein said halide iscalcium chloride.